The present invention has been made in view of the foregoing points, and is intended to propose an optical disk apparatus capable of reliably generating a track-cross signal even in an optical disk capable of large-capacity recording such as a DVD.
The above-described object is achieved by the present invention through the provision of an optical disk apparatus in which, if the track pitch between lands, where a track is formed of a land, or the track pitch between grooves, where a track is formed of a groove, is indicated by P, side beams scan in positions that are offset with respect to a main beam by approximately (¼+n)P or (¾+n)P in the radial direction of the optical disk; light-receiving means includes a light-receiving surface for receiving the return lights of the side beams, which is divided into first and second light-receiving regions by a dividing line corresponding to the direction in which the track extends, and a light-receiving surface for receiving the return light of the main beam, which is divided into third and fourth light-receiving regions by a dividing line corresponding to at least the direction in which the track extends; and signal processing means includes first subtracting means for generating a differential signal between light detection results obtained from the first and second light-receiving regions to generate a track-cross signal; second subtracting means for generating a differential signal between light detection results obtained from the third and fourth light-receiving regions; band-limiting means for removing a traverse component from the light detection result of a light-receiving region of the first and second light-receiving regions which is far from the third and fourth light-receiving regions; amplifying means for amplifying an output signal of the band-limiting means with a predetermined gain; and computing means for computing an output signal of the amplifying means with respect to an output signal of the second subtracting means so that, for each of the side beams, the light detection result of a light-receiving region of the first and second light-receiving regions which is far from the third and fourth light-receiving regions and the light detection result of a light-receiving region of the third and fourth light-receiving regions which is far from the first and second light-receiving regions are summed to generate a tracking error signal.
In the configuration of the present invention, therefore, the side beams scan in positions that are offset with respect to the main beam by approximately (¼+n)P or (¾+n)P in the radial direction of the optical disk; and a differential signal between light detection results obtained from the first and second light-receiving surfaces is generated to generate a track-cross signal, whereby, even when there is a small distance in reflectance between a land and a groove, the track-cross signal can be obtained because the amplitude is great. Therefore, a track-cross signal can be reliably generated in an optical disk capable of large-capacity recording, such as a DVD. Furthermore, the provision of second subtracting means for generating a differential signal between light detection results obtained from the third and fourth light-receiving regions, band-limiting means (low-pass filter) for removing a traverse component from the light detection result of a light-receiving region of the first and second light-receiving regions which is far from the third and fourth light-receiving regions, amplifying means for amplifying an output signal of the band-limiting means with a predetermined gain, and means for computing an output signal of the amplifying means with respect to an output signal of the second subtracting means so that, for each of the side beams, the light detection result of a light-receiving region of the first and second light-receiving regions which is far from the third and fourth light-receiving regions and the light detection result of a light-receiving region of the third and fourth light-receiving regions which is far from the first and second light-receiving regions are summed to generate a tracking error signal can effectively avoid occurrence of an offset voltage, and can further effectively avoid a change in signal level if the side beams scan in positions that are offset with respect to the main beam by approximately (¼+n)P or (¾+n)P in the radial direction of the optical disk, thus generating a tracking error signal.
The above-described object is further achieved by the present invention through the provision of a tracking control method in which, if the track pitch between lands, where a track is formed of a land, or the track pitch between grooves, where a track is formed of a groove, is indicated by P, a side beam scans in a position that is offset with respect to a main beam by approximately (¼+n)P or (¾+n)P in the radial direction of the optical disk; the return light of the side beam is received at a light-receiving surface which is divided into first and second light-receiving regions by a dividing line corresponding to the direction in which the track extends, and the return light of the main beam is received at a light-receiving surface which is divided into third and fourth light-receiving regions by a dividing line corresponding to at least the direction in which the track extends; a differential signal between light detection results obtained from the first and second light-receiving regions is generated to generate a track-cross signal; a differential signal between light detection results obtained from the third and fourth light-receiving regions is generated; a traverse component is removed from the light detection result of a light-receiving region of the first and second light-receiving regions which is far from the third and fourth light-receiving regions, and the result is amplified with a predetermined gain; and the result is computed with respect to the differential signal between the light detection results obtained from the third and fourth light-receiving regions so that, for each side beam, the light detection result of a light-receiving region of the first and second light-receiving regions which is far from the third and fourth light-receiving regions and the light detection result of a light-receiving region of the third and fourth light-receiving regions which is far from the first and second light-receiving regions are summed to generate a tracking error signal.
According to the present invention, therefore, a tracking control method can be achieved in which a track-cross signal can be reliably generated in an optical disk capable of large-capacity recording, such as a DVD, and a suitable tracking error signal can be further generated for such a configuration, thereby achieving stable seeking and other processing.
The above-described object is further achieved by the present invention through the provision of an optical disk apparatus in which, if the track pitch between lands, where a track is formed of a land, or the track pitch between grooves, where a track is formed of a groove, is indicated by P, a side beam scans in a position that is offset with respect to a main beam by approximately (¼+n)P or (¾+n)P in the radial direction of the optical disk; light-receiving means includes a light-receiving surface for receiving the return light of the side beam, which is divided into first and second light-receiving regions by a dividing line corresponding to the direction in which the track extends, and a light-receiving surface for receiving the return light of the main beam, which is divided into third and fourth light-receiving regions by a dividing line corresponding to at least the direction in which the track extends; and signal processing means includes first subtracting means for generating a differential signal between light detection results obtained from the first and second light-receiving regions to generate a track-cross signal; second subtracting means for generating a differential signal between light detection results obtained from the third and fourth light-receiving regions; band-limiting means for removing a traverse component from the light detection result of a light-receiving region of the first and second light-receiving regions which is near the third and fourth light-receiving regions; amplifying means for amplifying an output signal of the band-limiting means with a predetermined gain; and computing means for computing an output signal of the amplifying means with respect to an output signal of the second subtracting means so that, for each side beam, the light detection result of a light-receiving region of the first and second light-receiving regions which is far from the third and fourth light-receiving regions and the light detection result of a light-receiving region of the third and fourth light-receiving regions which is far from the first and second light-receiving regions are summed to generate a tracking error signal.
According to the configuration of the present invention, the side beam scans in position that is offset with respect to the main beam by approximately (¼+n)P or (¾+n)P in the radial direction of the optical disk; and a differential signal between light detection results obtained from the first and second light-receiving surfaces is generated to generate a track-cross signal, whereby, even when there is a small distance in reflectance between a land and a groove, the track-cross signal can be obtained because the amplitude is great. Therefore, a track-cross signal can be reliably generated in an optical disk capable of large-capacity recording, such as a DVD. Furthermore, the provision of second subtracting means for generating a differential signal between light detection results obtained from the third and fourth light-receiving regions, band-limiting means (low-pass filter) for removing a traverse component from the light detection result of a light-receiving region of the first and second light-receiving regions which is near the third and fourth light-receiving regions, amplifying means for amplifying an output signal of the band-limiting means with a predetermined gain, and means for computing an output signal of the amplifying means with respect to an output signal of the second subtracting means so that, for each side beam, the light detection result of a light-receiving region of the first and second light-receiving regions which is far from the third and fourth light-receiving regions and the light detection result of a light-receiving region of the third and fourth light-receiving regions which is far from the first and second light-receiving regions are summed to generate a tracking error signal can effectively avoid occurrence of an offset voltage, and can further effectively avoid a change in signal level if the side beam scans in position that is offset with respect to the main beam by approximately (¼+n)P or (¾+n)P in the radial direction of the optical disk, thus generating a tracking error signal.
The above-described object is further achieved by the present invention through the provision of a tracking control method in which, if the track pitch between lands, where a track is formed of a land, or the track pitch between grooves, where a track is formed of a groove, is indicated by P, a side beam scans in a position that is offset with respect to a main beam by approximately (¼+n)P or (¾+n)P in the radial direction of the optical disk; the return light of the side beam is received at a light-receiving surface which is divided into first and second light-receiving regions by a dividing line corresponding to the direction in which the track extends, and the return light of the main beam is received at a light-receiving surface which is divided into third and fourth light-receiving regions by a dividing line corresponding to at least the direction in which the track extends; a differential signal between light detection results obtained from the first and second light-receiving regions is generated to generate a track-cross signal; a differential signal between light detection results obtained from the third and fourth light-receiving regions is generated; a traverse component is removed from the light detection result of a light-receiving region of the first and second light-receiving regions which is near the third and fourth light-receiving regions, and the result is amplified with a predetermined gain; and the result is computed with respect to the differential signal between the light detection results obtained from the third and fourth light-receiving regions so that, for each side beam, the light detection result of a light-receiving region of the first and second light-receiving regions which is far from the third and fourth light-receiving regions and the light detection result of a light-receiving region of the third and fourth light-receiving regions which is far from the first and second light-receiving regions are summed to generate a tracking error signal.
According to the present invention, therefore, a tracking control method can be achieved in which a track-cross signal can be reliably generated in an optical disk capable of large-capacity recording, such as a DVD, and a suitable tracking error signal can be further generated for such a configuration, thereby achieving stable seeking and other processing.